[clang] [clang] Support -Wa, options -mmsa and -mno-msa (PR #99615)

[YunQiang Su via cfe-commits]

wzssyqa wrote:

I figure out another use case:
```
f:
        fadd.w  $w0,$w1,$w2
```

```
# ./bin/clang --target=mipsel-linux-gnu -mfp64 -Wa,-mmsa -fintegrated-as -c xx.s 
xx.s:2:2: error: instruction requires a CPU feature not currently enabled
        fadd.w  $w0,$w1,$w2
        ^
```
```
# ./bin/clang --target=mipsel-linux-gnu -mfp64 -Wa,-mmsa -fno-integrated-as -c xx.s
# Returns OK.
```

I guess that the use case of `-Wa,-mmsa` is to be compatible with some pre-exists software.


https://github.com/llvm/llvm-project/pull/99615